This invention relates to a process for preparing a palladium catalyst for purifying a waste gas. More particularly, the invention relates to a process for preparing a palladium catalyst comprising palladium particles uniformly and finely dispersed and supported on a carrier such as activated alumina for purifying carbon monoxide, hydrocarbons and the like contained in the waste gas such as an automotive exhaust gas from the internal combustion engine of automobiles etc., a waste gas from an industrial plant and a waste gas from such an electric apparatus for domestic use as a cooking stove, by completely oxidizing them.
Heretofore, a palladium-supported catalyst has been widely utilized as that for purifying the automotive exhaust gas from automobiles and the waste gas from the industrial plant, and especially in recent years the palladium-supported catalyst with a minimum amount of palladium particles having excellent catalytic performance supported on activated alumina has been developed.
Dinitrodiammine palladium (Pd(NH.sub.3).sub.2 (NO.sub.2).sub.2) is employed as one of the palladium sources for preparing the palladium catalyst. However, the dinitrodiammine palladium is fine powder which hardly dissolved in water or nitric acid at normal temperature. Accordingly, in order to increase the amount of the palladium metal deposited on the carrier, it is necessary to employ a suspended solution of colloidal palladium uniformly dispersed in water or nitric acid. If the suspended palladium is deposited on the carrier, it cannot be uniformly dispersed on the carrier so that the catalytic performance of the catalyst is insufficient.